By not letting your boss know, you are making it harder on yourself, and then leading to less productivity in the future, as opposed to getting better. Also it

By not letting your boss know, you are making it harder on yourself, and then leading to less productivity in the future, as opposed to getting better. Also it isn't that it actually costs the company money. They could very well make up for that lost time by hyper focusing and finishing it quickly later. So it could be the same result for the company but much more stressful for the person with ADHD.